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ORIGINAL ARTICLE Injuries in women’s professional soccer Br J Med: first published as on 25 March 2005. Downloaded from E Giza, K Mitho¨fer, L Farrell, B Zarins, T Gill ......

Br J Sports Med 2005;39:212–216. doi: 10.1136/bjsm.2004.011973

Objective: The injury data from the first two seasons of the Women’s United Soccer Association (WUSA) were analysed to determine the injury incidence, anatomic location of injuries, and relation of player position. Methods: Injury data on 202 players from eight teams during the first two seasons of the WUSA were prospectively collected and analysed. Results: A total of 173 injuries occurred in 110 players with an overall injury incidence rate of 1.93 See end of article for injuries per 1000 player hours. The incidence of injury during practice and games was 1.17 and 12.63 authors’ affiliations ...... per 1000 player hours, respectively. Of the injuries 82% were acute and 16% were chronic. Most of the injuries (60%) were located in the lower extremities. Strains (30.7%), sprains (19.1%), contusions (16.2%), Correspondence to: and fractures (11.6%) were the most common diagnoses and the knee (31.8%) and head (10.9%) were the Dr Eric Giza, Central Maine Orthopaedics, 690 most common sites of injury. Anterior cruciate ligament (ACL) injuries accounted for 4.6% of all injuries Minot Ave, Suite One, and the incidence of ACL tears was 0.09 per 1000 player hours (practice 0.04, game 0.90). Auburn, ME 04210, USA; suffered the most injuries (p,0.007). [email protected] Conclusion: We conclude that the injury incidence in the WUSA is lower than the 6.2 injuries per 1000 Accepted 15 June 2004 player hours found in the corresponding male professional league (Major League Soccer); however, knee ...... injuries predominate even in these elite female athletes.

occer is the world’s most popular organised with METHODS over 200 million males and 21 million females registered Injuries in this study were defined as those conditions which Swith the Fe`de`ration Internationale de were reported to and evaluated by the team physician or http://bjsm.bmj.com/ Association (FIFA). Epidemiological studies of male soccer athletic trainer. Each injury was subsequently reported to the players have identified an incidence of 10–35 injuries per league insurance company via a standardised ‘‘first report of 1000 game hours, equivalent to every player incurring one injury’’ form which is completed by the team trainer. All performance limiting injury per year.1–3 A review of the injury reports were verified by an examination by the team English professional male soccer leagues revealed that muscle physician. A detailed account of each injury is recorded in a strains (37%), ligament sprains (19%), and contusions (13%) general computer database and includes the date of injury, were the most common types of injury, and that the thigh injury location, diagnosis, injury description, and reimburse- (23%), knee (17%), and ankle (17%) were the most common ment cost. on September 30, 2021 by guest. Protected copyright. sites of injury.4 Studies on professional and amateur female For this investigation, the information in the database soccer players in Sweden have demonstrated an incidence of from all eight teams during the 2001 and 2002 pre-season, up to 24 injuries per 1000 game hours and up to seven season, and post-season was carefully reviewed and each injuries per 1000 practice hours.5–7 team trainer was contacted for further injury detail. Each Several studies have identified female soccer players as player signed a release of medical records form as part of having a higher incidence of knee injury and anterior cruciate their WUSA contract. A numerical code was assigned to each ligament (ACL) injury than males.8–11 In a prospective study player to protect confidentiality and permission for the use of of female soccer players, O¨stenberg and colleagues deter- the information was granted by the WUSA administration mined that general joint laxity and age over 25 are risk (Atlanta, GA) and American Specialty Insurance Services, factors for knee injury; however, no study has proven that Inc. (Roanoke, IN). a single etiology is responsible for female ACL injury Injury onset was determined by the detailed injury patterns.512 description, if available. An acute injury was defined as any In the United States 12.5–18.5 million people play soccer, injury or condition which had not existed prior to the date of with an estimated annual increase in participation of up to injury occurrence. A chronic injury was any injury with 21.8%.13 The growing popularity of soccer in the United States insidious progression that existed prior to the date of injury has led to the recent formation of professional male (1996) occurrence or an exacerbation of a previously existing and female soccer leagues (2001). The first women’s World condition. Cup soccer tournament was held in 1991 and the Women’s The average number of practices per season (125 sessions, United Soccer Association (WUSA) was the premier female average time 100 min) as recorded by team trainers and the soccer league in the world from 2001 to 2003. The interest of average number of games per season (21 games, average time female athletes in soccer necessitates continued investigation 90 min) for all teams was used to calculate the injury of injuries in order to identify injury patterns and effective incidence using the method described by Hawkins and means of prevention.14 The injury data from the first two seasons of the WUSA were analysed to determine the injury Abbreviations: ACL, anterior cruciate ligament; FIFA, Fe`de`ration incidence, anatomic location of injuries, and relation of Internationale de Football Association; MLS, Major League Soccer; player position. WUSA, Women’s United Soccer Association

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Fuller.15 The season runs from mid-February until August Knee injuries with additional post-season play. The season was divided into A total of 55 knee injuries occurred. Strains were the most pre-season (mid-February through March), early season common injury (15, 27.3%) followed by contusions (nine, (April through May 15th), midseason (May 16th through 16.4%), ACL injury (eight, 14.6%), sprains not involving the June), late season (July through end of season games in mid- ACL (seven, 12.7%), inflammation (seven, 12.7%), and Br J Sports Med: first published as on 25 March 2005. Downloaded from August), and post-season. All calculations were performed meniscal tear (five, 9.1%). Follow up investigation on the using Microsoft Excel (Microsoft, Seattle, WA) and Statistica diagnosis of knee ligament sprain was performed to (Statsoft, Tulsa, OK). x2 Statistical tests were used to analyse determine if an ACL injury had occurred. There were eight the data, with significance accepted at p,0.05 unless acute ACL tears during the two seasons, five from games and otherwise indicated. three from practices. Six of the eight were the result of non- contact situations, two were from collisions, and one was associated with a meniscal tear. The incidence of ACL tear RESULTS was 0.09 per 1000 player hours. ACL tear rates during games Injury incidence and practice were 0.90 and 0.04, respectively, per 1000 player A total of 173 injuries occurred over two seasons: 93 injuries hours. occurred during 2001 and 80 occurred during 2002. Of 202 players participating in the WUSA during the two seasons, Injury and time of season 110 suffered injuries; therefore 55% of players were injured. The distribution of all injuries is shown in fig 3. Significantly The overall injury incidence rate was 1.93 injuries per 1000 more injuries occurred during the latter portion of the player hours. Game versus practice information was available competitive season (p,0.018) and less occurred during the for 168 injuries, and the game and practice injury incidences post season (p,0.005). per 1000 player hours were 12.63 and 1.17, respectively. Player position Injury type and location Player position at the time of injury was recorded for 168 Injury type is summarised in fig 1 and injury location in fig 2. players. Midfielders sustained the most injuries (57, 34.1%) Strains (30.7%), sprains (19.1%), contusions (16.2%), and followed by defenders (47, 28.1%), strikers (38, 22.8%), and fractures (11.6%) were the most common diagnoses. The goalkeepers (26, 15.0%). Compared to all players, midfielders most common location was the knee (31.8%), followed by the suffered a significantly higher number of injuries (p,0.007); head (10.4%), ankle (9.3%), and foot (9.3%); 60% of the however, compared to other field players, injuries injuries occurred in the lower extremities. Of the injuries 82% did not reach a significant value. were acute (142), 16% were chronic (28), 0.6% were acute on chronic (one), and 1.4% were undetermined (two). DISCUSSION Of 18 head injuries, fractures of the nose and facial bones The overall incidence of injury in this study was 1.93 injuries

(five, 27.8%) and concussions (five, 27.8%) occurred most per 1000 player hours. The game incidence was 12.63 and the http://bjsm.bmj.com/ frequently. The remainder of the head injuries were lacera- practice incidence was 1.17. Our findings are consistent with tions and contusions. The incidence of concussions was 0.06 both the practice injury rates (range 1.5–7 per 1000 player per 1000 player hours. hours) and the game injury incidence (range 9.1–24 per 1000 Ankle sprains accounted for 86.7% of ankle injuries and player hours) found in other female soccer studies.5–7 Higher 7.51% (13) of all injuries. Eight of 13 ankle sprains involved a game injury rates have also been found in male soccer and plantarflexion/inversion mechanism. have been attributed to greater intensity of play during Of 20 fractures, the face and teeth (six, 30%) and the foot games.41617

(five, 25%) were the most frequent sites of injury. Stress Morgan and Oberlander investigated the injuries of the on September 30, 2021 by guest. Protected copyright. fractures (one tibia, one first metatarsal) accounted for two inaugural season of Major League Soccer (MLS) and found fractures (10%) and the remaining 18 were the result of acute an overall injury rate of 6.2 injuries per 1000 player hours.1 In situations. accordance with their method study, we included all injuries,

75 Number Percent 60

45

30

15

0

Hernia Other Sprain Strain Fracture Contusion Concussion Laceration Chondral injury Meniscus tear

Tendonitis/inflammation

Figure 1 Description of injury. There were five isolated meniscal tears. Another tear was associated with an ACL injury and was grouped with sprains.

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75 Number Percent

60 Br J Sports Med: first published as on 25 March 2005. Downloaded from

45

30

15

0

Eyes Hip Foot Leg Ankle Chest Head Knee Thigh Other Abdomen Spine/back Pelvis/sacrum Upper extremity

Figure 2 Location of Injury location. such as upper extremity and facial injuries, and not just those tournaments, and found a 35% total decrease in total injuries which resulted in time lost from play. Our finding of 1.93 with a 50% reduction in female injuries.22 Elias identified a injuries per 1000 h in the WUSA is important as it may gradual decrease in the incidence of injuries in female soccer indicate that professional female soccer players in the United players from 1987 to 1997 in a recent study in which injuries States suffer less injuries than their male counterparts. from a youth soccer tournament were recorded prospectively http://bjsm.bmj.com/ Although soccer epidemiology studies in the 1970s and over 10 years.23 Data from the 1999–2000 NCAA injury early 1980s18 19 showed that females had a higher injury rate, surveillance system revealed a nearly equal game injury rate age and skill level may have more of an influence on injury in males (20.75 per 1000 player exposures) and females incidence than gender alone. In a 5 day invitational tourna- (18.75 per 1000 player exposures)24 25; therefore, improved ment in 1985 with over 6000 players, Schmidt-Olsen et al training, fitness, and skills may contribute to the low found that females aged 17–19 had a much higher injury rate incidence found in this investigation. (47.1 per 1000 h) compared to males in the same age group Five concussions occurred during the two seasons (20.6 per 1000 h).20 In 1984, Maehlum et al studied injuries at (approximately one concussion every 15.3 weeks) and all on September 30, 2021 by guest. Protected copyright. the Norway Cup, one of the world’s largest youth club five situations involved player to player collisions. Boden et al tournaments, and found the injury rate to be twice as high in determined the incidence of concussion in female collegiate females as in males.21 In 1999, Maehlum et al compared soccer players to be 0.44 per 1000 athlete exposures, that is values from the 1984 tournament to the 1993 and 1997 approximately one concussion every 13.5 weeks or one concussion per team per year.26 Boden et al also found that 76% of concussions resulted from player to player or player to object (goal post, elbow, sideline advertisement) contact and Injuries Asterisk denotes statistical significance 70 only 24% resulted from head to ball contact from a ball kicked at full force at a close range.26 The relationship of 60 chronic traumatic brain injury and soccer remains a controversial topic, as Tysvaer and Matser et al have shown in separate studies that soccer players exhibit deficiencies in 50 memory and planning compared to controls.27 28 In contrast, a recent study used similar neuropsychological tests to those 40 used by Matser et al, and showed that soccer related concussions were not associated with impaired neurocogni- 30 tive function.29 Jordan and colleagues compared 20 national soccer team members to controls and found no differences in 20 brain MRI findings.30 The finding of an increased number of injuries during the 10 late season is consistent with other studies of both male and female soccer injuries.4731The increase in injuries during the 0 Pre- Early Mid- Late Post end of the season could be due to deconditioning or an season season season season season increase in play intensity for play-off or tournament positions. The lower incidence in post-season play is expected Figure 3 Relationship of time of season with injury occurrence. as fewer players participate.

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What is already known on this topic What this study adds

Information on professional female players is limited, and This is the first prospective study of female professional studies on amateur and youth females have identified soccer. We have demonstrated that the injury rate in the practice and game injury rates of 1.5–7 and 9.1–24 per WUSA is lower than its corresponding male professional Br J Sports Med: first published as on 25 March 2005. Downloaded from 1000 player hours, respectively. Female soccer players have league. We have found that the knee is the most common a four times higher risk of knee and ACL injury than males. location for injury even in these elite female soccer players.

...... The knee was the most common injury site in our study Authors’ affiliations (31.8%), and this finding is consistent with the study of E Giza, Central Maine Orthopaedic Group, Auburn, ME, USA female soccer players by O¨stenberg et al.5 An awareness of the K Mitho¨fer, Hospital for Special Surgery, New York, NY, USA propensity of knee injuries in female soccer players is L Farrell, Boston Breakers, Boston, MA, USA particularly important for the team physician and team B Zarins, T Gill, Massachusetts General Hospital, Boston, MA, USA trainer, as it has been shown that 12 years post-injury, 34% Competing interests: none declared of previous female soccer players in Sweden who suffered an ACL injury have radiographic changes consistent with 32 REFERENCES osteoarthritis. 1 Morgan B, Oberlander M. An examination of injuries in major league soccer. An overall incidence of 0.09 ACL injuries per 1000 player Am J Sports Med 2001;29:426–30. hours was found in this study. Five of the eight ACL injuries 2 Hawkins R, Fuller C. A prospective epidemiological study of injuries in four occurred during games (0.90 ACL injures per 1000 game English professional football clubs. Br J Sports Med 1999;33:196–203. 3 Dvorak J, Junge A. Football injuries and physical symptoms. Am J Sports Med hours). Bjordal and colleagues found an incidence of 0.10 per 2000;28:S3–9. 1000 h, and other investigators found 0.31 ACL injuries per 4 Hawkins R, Hulse M, Wilkinson C, et al. The Medical 1000 h.533 Only two of eight ACL injuries involved contact Research Programme: an audit of injuries in professional football. Br J Sports Med 2001;35:43–7. situations, and although the number of ACL injures is too 5 O¨ stenberg A, Roos H. Injury risk factors in female European football. A small to reach statistical significance, these results are prospective study of 123 players during one season. 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Am J Sports Med others have shown that pre-season conditioning and fitness 1995;23:694–701. http://bjsm.bmj.com/ can reduce overall injury rates.35 38 39 The elite soccer players 9 Roos H, Ornell M, Gardsell P, et al. Soccer after ACL injury - an incompatible combination? Acta Orthop Scand 1995;66:107–12. in this study have achieved the highest level of play possible 10 Engstrom B, Forssblad M, Johansson C, et al. Does a major knee injury in female soccer; therefore, our findings of a low injury rate definitely sideline an elite soccer player? Am J Sports Med 1990;18:101–5. could reflect the high level of fitness needed to participate in 11 Lindenfeld T, Schmitt D, Hendy M, et al. Incidence of injury in indoor soccer. Am J Sports Med 1994;22:364–71. the WUSA and the impact of proper pre-season strengthen- 12 Ireland ML. The female ACL: why is it more prone to injury? Orthop Clin North ing and training. 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Med 1984;18:186–90. 22 Maehlum S, Daljord O, Hansen KJ. Frequency of injuries in youth soccer. Med Sci Sports 1999;31:S401. 23 Elias SR. 10-year trend in USA Cup soccer injuries: 1988–1997. Med Sci SUMMARY Sports Exerc 2001;33:359–67. A preliminary study of the injuries among 202 elite female 24 National Collegiate Athletic Association. Injury surveillance system, women’s soccer players has shown that the incidence of injury in the soccer. Indianapolis, IN: NCAA, 2000. 25 National Collegiate Athletic Association. Injury surveillance system, men’s WUSA is similar to that found in the existing literature on soccer. Indianapolis, IN: NCAA, 2000. female soccer injuries, and that rates during game play are 26 Boden B, Kirkendall D, Garrett W. Concussion incidence in elite college much higher than during practice. Injures about the knee are soccer players. Am J Sports Med 1998;26:238–41. most common and continue to predominate even in these 27 Tysvaer A. Head and neck injuries in soccer. Sports Med 1992;14:200–13. 28 Matser E, Kessels A, Lezak M, et al. Neuropsychological impairment in high-level athletes. The results of this study accentuate the amateur soccer players. JAMA 1999;282:971–3. importance of a more comprehensive analysis of the injury 29 Guskiewicz KM, Marshall SW, Broglio SP, et al. No evidence of impaired patterns in these elite athletes to enable the creation of neurocognitive performance in collegiate soccer players. Am J Sports Med 2002;30:157–62. prevention protocols for professional, amateur, and youth 30 Jordan S, Green G, Galanty H, et al. Acute and chronic brain injury in United female soccer players. States National Team soccer players. Am J Sports Med 1996;24:205–10.

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31 Ekstrand J, Hilding J. The incidence and differential diagnosis of acute groin pain in male soccer players. Scand J Med Sci Sports 1999;9:98–103...... 32 Lohmander LS,O¨ stenberg A, Englund M, et al. High prevalence of knee COMMENTARY osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum This original article provides some valuable data on the 2004;50:3145–52. incidence of injury in professional female soccer players and

33 Bjordal JM, Arnly F, Hannestad B, et al. Epidemiology of anterior cruciate Br J Sports Med: first published as on 25 March 2005. Downloaded from ligament injuries in soccer. Am J Sports Med 1997;25:341–5. raises some interesting arguments regarding gender differ- 34 Delfico A, Garrett W. Mechanisms of injury of the ACL in soccer players. Clin ences and the influence that professionalism has had on the Sports Med 1998;17:779–85. development of the sport. The difference in injury rates may 35 Heidt RS Jr, Sweeterman LM, Carlonas RL, et al. Avoidance of soccer injuries with preseason conditioning. Am J Sports Med 2000;28:659–62. well reflect the differing levels of intensity between males 36 Hewett TE, Lindenfeld TN, Riccobene JV, et al. The effect of and females at the elite end of the sport. However, there may neuromuscular training on the incidence of knee injury in female also be some interesting lessons to be learnt by the male athletes. A prospective study [comment]. Am J Sports Med 1999;27:699–706. soccer population from the physical and mental preparation 37 Junge A, Dvorak J, Chomiak J, et al. Medical history and physical findings in of their female counterparts to assist in reducing the risk of football players of different ages and skill levels. Am J Sports Med injury. 2000;28:S16–21. 38 Junge A, Rosch D, Peterson L, et al. Prevention of soccer injuries: a prospective intervention study in youth amateur players. Am J Sports Med 2002;30:652–9. S Drawer 39 Ekstrand J, Gillquist J, Liljedahl S. Prevention of soccer injuries. Am J Sports UK Sport, 40 Bernard Street, London WC1N 1ST, UK; Med 1983;11:116–20. [email protected]

ELECTRONIC PAGES ...... Online original articles he following electronic only articles are published in conjunction with this issue of BJSM (see also pages 189 Tand 211)

The repeatability and criterion related validity of the however, these results show that when applying an arguably 20 m multistage fitness test as a predictor of maximal more appropriate analysis method, the MFT does not provide oxygen uptake in active young men valid predictions of Vo2max.

(Br J Sports Med 2005;39:e19) http://bjsm.bmjjournals.com/ http://bjsm.bmj.com/ S-M Cooper, J S Baker, R J Tong, et al cgi/content/full/39/1/e19 Objective: To investigate the repeatability and criterion related validity of the 20 m multistage fitness test (MFT) for Motivation and satisfaction among polyclinic predicting maximal oxygen uptake (Vo2max) in active young volunteers at the 2002 Winter Olympic and men. Methods: Data were gathered from two phases using 30 J C Reeser, R L Berg, D Rhea, et al subjects (x¡s; age = 21.8¡3.6 years, mass = 76.9¡10.7 kg, Background: The Olympic and Paralympic Games rely stature = 1.76¡0.05 m). MFT repeatability was investigated heavily on volunteers to provide many essential services, in phase 1 where 21 subjects performed the test twice. The including medical care of athletes. on September 30, 2021 by guest. Protected copyright. MFT criterion validity to predict Vo2max was investigated in Objective: This preliminary investigation sought to char- phase 2 where 30 subjects performed a continuous incre- acterise the motivational influences and factors responsible mental laboratory test to volitional exhaustion to determine for the satisfaction of Olympic and Paralympic healthcare Vo2max and the MFT. volunteers. Results: Phase 1 showed non-significant bias between Methods: The 2002 Winter Games polyclinic healthcare the two applications of the MFT (x¯diff¡sdiff = 20.4¡ volunteers were asked to complete a questionnaire designed 1.4 ml kg21 min21;t=21.37, p = 0.190) with 95% limits to elicit information about their motives for volunteering and of agreement (LoA) ¡2.7 ml kg21 min21 and hetero- the factors that contributed to their satisfaction with their scedasticity 0.223 (p = 0.330). Log transformation of these volunteer experience. data reduced heteroscedasticity to 0.056 (p = 0.808) with Results: There was no significant difference in the motiva- bias 20.007¡0.025 (t = 21.35, p = 0.190) and LoA¡0.049. tion or satisfaction summary scores based on event worked. Antilogs gave a mean bias on the ratio scale of 0.993 and There was a strong positive correlation between motivation random error (ratio limits) 6/41.050. Phase 2 showed and satisfaction. Physician respondents had a lower mean that the MFT significantly underpredicted Vo2max (x¯diff¡ motivation score than did non-physician volunteers. 21 21 sdiff = 1.8¡3.2 ml kg min ; t = 3.10, p = 0.004). LoA Conclusions: There were no significant motivational differ- were ¡6.3 ml kg21 min21 and heteroscedasticity 0.084 ences between Olympic and Paralympic volunteers, but there (p = 0.658). Log transformation reduced heteroscedasticity were several differences noted between physician and non- to 20.045 (p = 0.814) with LoA¡0.110. The significant physician volunteers. The 2002 polyclinic volunteers appear systematic bias was not eliminated (x¯diff¡sdiff = 0.033¡ to have been motivated by a complex process best described 0.056; t = 3.20, p = 0.003). Antilogs gave a mean bias of as ‘‘enlightened self interest,’’ and all were generally well 1.034 with random error6/41.116. satisfied with their experience. These results may assist Conclusions: These findings lend support to previous organisers of future Games in selecting appropriately investigations of the MFT by identifying that in the motivated volunteer personnel and creating rewarding work population assessed it provides results that are repeatable environments for them. but it routinely underestimates Vo2max when compared to (Br J Sports Med 2005;39:e20) http://bjsm.bmjjournals.com/ laboratory determinations. Unlike previous findings, cgi/content/full/39/1/e20

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